Disaster recovery is an availability solution for recovering all or a portion of a datacenter at a recovery site from replicated data. For example, a virtual machine (VIVI) or logical storage device within a source datacenter site may be configured for replication to a destination datacenter site. When a VM is initially configured for replication, a replication process performs a full synchronization operation. During the full synchronization, the replication process copies all of the data from the source VM to the destination site. If, however, the source VM is large or if the bandwidth of the network connection between the source and destination is low, the initial full synchronization might take a long time. As a result, an administrator may choose to create a seed copy of the VM at the destination site. For example, the administrator may clone or otherwise export a copy of the source virtual machine to a removable storage medium, which is physically transported to the destination site to seed the replication at the destination site. When a replication is configured using a seed copy, the replication process does not simply copy all of the data from the source VM to the destination site during the initial full synchronization. Instead, the replication process performs the full synchronization by comparing the source and destination copies of the data. For example, this comparison may include each of a source site and destination site reading and generating checksums of corresponding portions of storage within the source site and the destination site, respectively. The destination site transmits its checksums to the source site. The source site compares the checksums to determine if any of the checksums from the destination site do not match the corresponding checksums from the source site, e.g., due to changes that occurred subsequent to making the initial copy. When a checksum does not match, the source site reads and transmits, to the destination site, the data from the portion of storage that lacks a matching checksum. The destination site receives and writes the data to the destination storage to bring the destination site into synchronization with the source site.
Additionally, other replication configurations may result in synchronization between the source and destination. For example, when reversing the direction of protection, a replication process may use an original source copy of a VM (that is becoming the destination copy) as a seed.